This invention relates to a dual axle system for large vehicles and in one embodiment in which the system is steerable. The invention is particularly useful for large off-road vehicles, such as trucks used for carrying extremely large loads. These type of trucks are customarily used in surface and open pit mining, earth moving and so forth. Such large off-road trucks are required not only to carry large loads but to move at fairly high speeds and typically over rough ground, that is, they do not typically travel on paved roads. Even in projects where some portions of the vehicle travel is over road surfaces that are maintained, the usual application includes at least some surfaces that are not maintained. In other words, these large off-road trucks must carry heavy loads at fairly high speeds over uneven terrain. For this reason, the axle arrangement and suspension system must be arranged to achieve two basic objectives, that is, support extremely heavy loads and, second, to provide suspension and mounting systems for the axle assemblies that support such heavy loads without transferring to the vehicle frame excessive shock from uneven terrain.
For reference to types of vehicles to which the present disclosure relates, reference may be had to U.S. patent application Ser. No. 07/650,442, entitled "Steerable Rear Dual Axle System For Large Trucks" now U.S. Pat. No. 5,088,570. Such disclosure describes a dual axle system for large trucks, as does the present disclosure. The dual axle system described in application Ser. No. 07/650,442 is steerable, that is, provision is made for changing the angular relationship between dual rear axles to coordinate with the vehicle front steering system. The present disclosure also provides a system having a forward and a rearward rear axle in which the rearward rear axle is steerable.
It is an object of this disclosure to provide an improved dual rear axle assembly for large vehicles that, in one embodiment, is steerable. More particularly, an object of this invention is to provide a dual rear axle assembly specifically useful for axles that include large cylindrical axle housings designed for mounting therein electric drive systems, with axles extending from the electric drive systems. An important aspect of this disclosure is the provision of a dual rear axle assembly for large trucks including forward and rearward axle housings wherein the axle housings are supported in a manner to permit independent motion in vertical planes of the axles. In a preferred embodiment of the dual axle system one rear axle is steerable relative to the other.